Re: [Xen-devel] [PATCH V9 for-4.5 4/4] xen: Handle resumed instruction based on previous mem_event reply

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.09.14 at 10:29, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> --- a/xen/include/public/mem_event.h
> +++ b/xen/include/public/mem_event.h
> @@ -31,11 +31,19 @@
>  #include "io/ring.h"
>  
>  /* Memory event flags */
> -#define MEM_EVENT_FLAG_VCPU_PAUSED  (1 << 0)
> -#define MEM_EVENT_FLAG_DROP_PAGE    (1 << 1)
> -#define MEM_EVENT_FLAG_EVICT_FAIL   (1 << 2)
> -#define MEM_EVENT_FLAG_FOREIGN      (1 << 3)
> -#define MEM_EVENT_FLAG_DUMMY        (1 << 4)
> +#define MEM_EVENT_FLAG_VCPU_PAUSED     (1 << 0)
> +#define MEM_EVENT_FLAG_DROP_PAGE       (1 << 1)
> +#define MEM_EVENT_FLAG_EVICT_FAIL      (1 << 2)
> +#define MEM_EVENT_FLAG_FOREIGN         (1 << 3)
> +#define MEM_EVENT_FLAG_DUMMY           (1 << 4)
> +/*
> + * Emulate the fault-causing instruction (if set in the event response 
> flags).
> + * This will allow the guest to continue execution without lifting the page
> + * access restrictions.
> + */
> +#define MEM_EVENT_FLAG_EMULATE         (1 << 5)
> +/* Same as MEM_EVENT_FLAG_EMULATE, but with write operations disabled. */

As we've gone through this incrementally suppressing more and more
operations, I think you should be very explicit here and say "...
with write operations or operations potentially having side effects
(like memory mapped or port I/O) disabled".

Jan

> +#define MEM_EVENT_FLAG_EMULATE_NOWRITE (1 << 6)
>  
>  /* Reasons for the memory event request */
>  #define MEM_EVENT_REASON_UNKNOWN     0    /* typical reason */
> -- 
> 1.7.9.5




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